A system for decoding serial data is provided wherein binary digits of a data stream are converted into parallel data format. Specifically, decoding of remote control function data is provided without using synchronized clocks in the transmitter and receiver units.
Remote control systems for television receivers are in wide-spread use. Since 1974, The Magnavox Company has sold under the trademark name "Star" System television receivers with accompanying remote control units. The earlier remote control units were the ultrasonic type wherein a viewer at a distance away from the television receiver affects certain limited controls of the television receiver by sending ultrasonic signals across the room to the television receiver. The ultrasonic system has bandwidth limitations as well as problems associated with false triggering due to extraneous sources of ultrasonic energy.
Recently, infared light has been proposed as the medium for conveying information to a television receiver from a distance away from the receiver. The infared light system is more secure than the ultrasonic system, and further includes an increased capability for carrying more commands to the television receiver.
In conjunction with the use of infared light as a signaling medium, a Telco code converter for converting keyboard selected function data into a serial code has become available. N. V. Philips Company has manufactured and sold Telco code converters which provide a serial binary data stream including a start code followed by data bits. When the viewer selects on a hand-held remote control keyboard a particular function to be executed, such as on/off, volume up, volume down, or channel selection, the Telco code converter produces a serial code including the start code identifying the particular function selected.
At the receiver, the serial data which occurs in bursts of infared radiation is decoded into corresponding binary ones and zeros. The receiver executes the decoded binary data and the selected function is executed.
The serial data transmitted by a remote user of the television receiver occurs at an irregular interval at the discretion of the user. The serial data must be converted and placed into a parallel format for execution. Recently, microprocessors have been employed to accomplish control of television receiver functions such as tuning, volume, power/on, etc. In microprocessor controlled television receivers, the command for controlling the receiver passes through the microprocessor for execution. It is therefore desirable to provide for direct sampling and conversion of the received serial data by the microprocessor whereby the data can be executed once decoded.